Boron-loaded liposomes in the treatment of hepatic metastases: preliminary investigation by autoradiography analysis.

Boronophenylalanine (BPA)-loaded conventional and stabilized liposomeswere prepared by the reversed phase evaporation method to treat livermetastases by boron neutron capture therapy. Conventional vesicles were composed of phosphatidylcholine and cholesterol, molar ratio 1:1. To obtain stealth liposomes, GM1 or PEG were included in the lipidic bilayer at a concentration of 6.67 or 5 mol%, respectively. Large unilamellar vesicles were formulated encapsulatingBPA in the liposome aqueous compartment as a complex with fructose;BPAfree base also was embedded into the lipidic bilayer. In vivo experiments were carried out after intravenous injection of liposome suspensions in BD-IX strain rats in which liver metastases had been induced. Alpha particle spectroscopy associated with histological analysis was performed to visualize boron spatial distribution in liver. Simultaneously, tissue boron concentrations
were determined using inductively coupled plasma-mass spectroscopy. Results showed that PEG-modi ed liposomes accumulated boron in therapeutic concentrations (> 30 ¹g boron/g
tissue) in metastatic tissue. The PEG-liposomes could be further explored in enhancing boron delivery to tumor cells.